title: Microfluidic droplet-based liquid-liquid extraction and on-chip IR spectroscopy detection of cocaine in human saliva.
abstract: We present a portable microsystem to quantitatively detect cocaine in human saliva. In this system, we combine a microfluidic-based multiphase liquid-liquid extraction method to transfer cocaine continuously from IR-light-absorbing saliva to an IR-transparent solvent (tetrachloroethylene) with waveguide IR spectroscopy (QC-laser, waveguide, detector) to detect the cocaine on-chip. For the fabrication of the low-cost polymer microfluidic chips a simple rapid prototyping technique based on Scotch-tape masters was further developed and applied. To perform the droplet-based liquid-liquid extraction, we designed and integrated a simple and robust droplet generation method based on the capillary focusing effect within the device. Compared to well-characterized and commonly used microfluidic H-filters, our system showed at least two times higher extraction efficiencies with potential for further improvements. The current liquid-liquid extraction method alone can efficiently extract cocaine and pre-concentrate the analytes in a new solvent. Our fully integrated optofluidic system successfully detected cocaine in real saliva samples spiked with the drug (500 μg/mL) and allowed real time measurements, which makes this approach suitable for point-of-care applications.
authors.affiliation: Sensors, Actuators and Microsystems Laboratory, Ecole Polytechnique Fédérale de Lausanne, Neuchâtel, Switzerland. philip.waegli@a3.epfl.ch
authors.forename: Philip
authors.initials: P
authors.lastname: Wägli
authors.forename: Yu-Chi
authors.initials: YC
authors.lastname: Chang
authors.forename: Kerstin
authors.initials: K
authors.lastname: Hans
authors.forename: Alexandra
authors.initials: A
authors.lastname: Homsy
authors.forename: Lubos
authors.initials: L
authors.lastname: Hvozdara
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Herzig
authors.forename: Markus
authors.initials: M
authors.lastname: Sigrist
authors.forename: Nico F
authors.initials: NF
authors.lastname: de Rooij
mesh_terms: D053000:Analytic Sample Preparation Methods; D003042:Cocaine / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification*; D006801:Humans; D059625:Liquid-Liquid Extraction / Q000379:methods*; D046210:Microfluidic Analytical Techniques / Q000379:methods*; D012463:Saliva / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods*
chemical_list: D003042:Cocaine